Question: Can you describe how a simple payback calculator for a green building retrofit project works?
In determining simple payback for a green building retrofit project, the cost of the project is the numerator and the annual savings (such as energy or electricity costs) would be in the denominator.
For instance if $10,000.00 was invested to install an energy management system, and this resulted in annual savings of $3000.00, your equation would be 10000/3000 = 3.33 (or 3.33 years to breakeven on the investment).
So the formula is: Payback (years)=Cost/Annual Savings
More Advanced Building Calculations:
More advanced calculations for green building projects may be necessary. These calculations include discounted cash flow (DCF), internal rate of return (IRR), energy modeling, savings to investment ratios, U-factor, etc.
For example in measuring energy efficiency performance of windows, specific window performance information (such as u-factor and shading coefficient/solar heat gain coefficient) are becoming more important aspects of project construction documents.
To aid designers and builders in preparing this information, Pilkington has recently redesigned and updated its Sun Management and Thermal Stress online calculators to include an interactive format, new products, updated performance data and improved features.